He barely wrote songs when he was in DM. That was mostly done by Martin.
But Alan def did a good share of experimenting with sound which made DM
original. However, it’s understandable, he wanted to try something new and
went solo.

The person I was replying to expressed hopes that Alan would return to
Depeche Mode. Alan never seems to hear the end of that. A biorgraphy of
Depeche Mode was released a few years ago. In it, Alan stated bluntly that
he never fit in and that his work was never given a lot of appreciation. He
reached the breaking point after the Devotional tour.